1. Filed of the Invention
The present invention relates to an electrode for a rechargeable lithium battery and a rechargeable lithium battery utilizing the same.
2. Description of Related Art
Recently, rechargeable lithium batteries have been extensively developed. Such rechargeable lithium batteries exhibit battery characteristics, such as charge-discharge voltage, charge-discharge cycle life characteristics and storage characteristics, which depend largely upon the types of the electrode active materials used.
The use of lithium metal as the negative active material enables construction of batteries which exhibit high energy densities, both per weight and per volume. However, the lithium deposited on charge grows into dendrite, which could cause problematic internal short-circuiting (Solid State Ionics, 113–115, p 57(1998)).
On the other hand, rechargeable lithium batteries are reported using an electrode composed of aluminum, silicon, tin or the like which alloys electrochemically with lithium during charge (Japanese Patent Laid-Open No. Hei 10-255768).
However, since these active materials which store lithium via alloying expand and shrink in volume as they store and release lithium, they are pulverized during charge and discharge or caused to separate from the current collector. This results in the failure to obtain satisfactory charge-discharge cycle characteristics, which has been a problem.
An electrode, for a rechargeable lithium battery, which incorporates a noncrystalline or microcrystalline silicon thin film deposited on a copper foil or other current collector by a CVD or sputtering technique has been reported to exhibit satisfactory charge-discharge cycle characteristics because of good adhesion of the thin film of active material to the current collector (International Publication No. WO 01/31720A1 etc.).
However, in such an electrode for a rechargeable lithium battery, due to the improved adhesion between the current collector and the thin film of active material, a large stress is produced in the current collector as the thin film of active material expands and shrinks during charge and discharge. This occasionally results in the occurrence of deformation, such as wrinkle formation in the current collector. As the current collector undergoes wrinkling or other type of deformation, a proportion of a battery volume that is occupied by the electrode when housed in the battery increases. As a result, an energy density per volume of the battery is problematically reduced.